Wavelength locker

Abstract

An apparatus and method for calculating the frequency of the light.

The invention claimed is: 
     
       1. A method comprising:
 reading a temperature of a wavelength filter of a silicon photonics chip using a temperature sensor of the silicon photonics chip; wherein the wavelength filter is a ring-resonator add drop filter; wherein the temperature sensor and a heater are proximate to the wavelength filter on the silicon photonics chip; wherein the heater is enabled to change the temperature of the wavelength filter to change a wavelength of the wavelength filter; 
 measuring light dropping from the ring resonator add drop filter using a first photodetector optically coupled to the ring resonator add drop filter; wherein the first photodetector is enabled to measure light passing through the ring-resonator add-drop filter; 
 measuring the light dropping from the ring resonator add drop filter using a second photodetector optically coupled to the ring resonator add drop filter; and 
 inputting the measured light from the first photodetector into a control system; 
 inputting the measured light from the second photodetector into the control system; and 
 tuning a laser using the control system to make the output of measured light of the first photodetector and the second photodetector to be equal. 
 
     
     
       2. The method of  claim 1  wherein the temperature sensor is a diode sensor. 
     
     
       3. The method of  claim 1  wherein the temperature of the wavelength filter is used to place a slope of the wavelength filter response at a desired wavelength. 
     
     
       4. The method of  claim 1  further comprising locking the temperature of the wavelength filter; and
 locking the laser to the wavelength filter. 
 
     
     
       5. The method of  claim 1  wherein tuning of the laser includes locking the laser on a slope of the wavelength filter according to a wavelength of the laser.